The invention relates to a flowmeter for regulating and monitoring the flow of sealing fluid to be conducted to a seal of a rotating shaft, the meter comprising a body, a sealing fluid metering channel arranged in the body, a sealing fluid inlet on a first end side of the metering channel and a sealing fluid connection towards the seal on a second end side of the metering channel, a control valve for regulating the flow of sealing fluid, a non-return valve for preventing the sealing fluid from flowing back to the flowmeter, a regulating and monitoring mechanism comprising a metering cone placed in the metering channel and metering the flow of the sealing fluid, the cross section of the cone tapering in the flow direction, a float movably arranged in the metering channel about the control cone, the float having an opening for the metering cone, and a spring placed in the metering channel and acting against the flow direction on the float, the sealing fluid flowing through the opening between the float and the metering cone, and a cleaning means which is placed in the metering channel between the float and the metering channel inlet side end to extend to the inner surface of the metering channel and which is movable in the metering channel by means of actuating means extending outside the metering channel.
A flowmeter of this kind is used, for instance, in pulp and paper industries, chemical industry, oil and gas industries and food industry, in monitoring seals that are typically plait gaskets or mechanical rotary seals. It is the function of the sealing fluid to lubricate the seal's sliding surfaces and to extract extra heat from the seal. The sealing fluid to be used is generally water.
Prior art flowmeters are manufactured such that the meter itself and its cleaning actuator which enables the meter's volume flow indication area to be cleaned, are integrated in a plastic body. There exist various options for cleaning methods: those to be pressed, pulled or based on reciprocating movement. Likewise, there are metering cones of different types: a conventional rotameter model, one provided with a buoyant float, a spring-loaded float with a metering cone in the middle thereof, a spring-loaded float with a cone machined in the cylinder hole thereof, a spring-loaded float and a cone fixedly secured to the cleaning means (e.g. see Finnish patent 100360). Known meters also comprise a non-return valve that is integrated with the body. A throttling area and an indication area of a spring-loaded float metering the flow are typically arranged in the same end of the float.
A problem with the flowmeters is that when a seal failure has occurred, industrial product to be treated starts flowing in the vicinity of the seal towards the flowmeter connection to the seal. This industrial product is liquid that may contain acids, bases and various particles. In known flowmeters, such as the one set forth in the above Finnish patent, a non-return valve is placed apart from the metering channel, generally in connection with the sealing fluid connection to the seal such that the motion of the non-return valve is perpendicular to the components in the metering channel. Particles in the industrial fluid that flow to the non-return valve through the connection towards the seal clog and jam it. When the non-return valve is jammed, the seal remains without sealing fluid, and consequently lubrication and cooling thereby is defective. Sooner or later the seal fails. When the seal failure is detected, the damaged seal is replaced by a new one, but the non-return valve clogged with particles from the industrial fluid will not necessarily be cleaned, and therefore the clogged valve prevents sealing fluid's access to the seal and hence the new seal will also get damaged. Generally, it is not until that a flowmeter function failure is detected, and thereafter the flowmeter will be disassembled and the non-return valve cleaned.
In addition, the known non-return valves are often made of rubber or plastic, whereby failure through acids or high temperature poses a great risk to safety. Moreover, the non-return valves require a light pressure to open, which causes pressure loss in the flowing fluid. This problem is obvious particularly in plants having low sealing water pressures. Currently it is possible for industry to use condensation water, for instance, as the sealing fluid, whereby the temperature and the pressure of the sealing fluid may be high.